Assignment of the ferriheme resonances of the high-spin forms of nitrophorins 1 and 4 by [super 1]H NMR spectroscopy: Comparison to structural data obtained from X-ray crystallography

A study was conducted to investigate in detail the [super 1]H NMR spectra of the ferriheme center and nearby protein residues in the high- and low-spin forms of the nitrophorins (NPs) from Rhodnius prolixus. The structures of the ferriheme complexes in terms of the orientation of the histidine imidazole ligand orientations depends on the heme cavity shape and could be altered by mutation of amino acids with side chains (phenyl vs tyrosyl) near the potential position where a heme vinyl group would be in one of the isomers.